Suppose that a cell membrane receptor is stimulated (by a hormone, say, or a neurotransmitter) at time t = 0, and that the concentration of activated receptor, R

∗

, is given by the following function of time R

∗

(t) =

VRt KR + t

.

This receptor then activates another protein inside the cell (such as a G protein), to form an activated protein. Suppose that the concentration of activated G protein, G

∗

, is given by the following function of R

∗

G ∗
(R ∗
) = VG R ∗
KG + R∗
.

a. What is the maximum concentration of activated receptor?

b. What is G ∗
as a function of time?

c. What is the maximum value of G ∗
?

d. If you wanted to make more G ∗ would it be more effective to increase VG or to increase VR? Explain your answer.